This invention relates to certain metal-containing catalysts and to methods for preparing metal-containing catalysts for alkylene oxide polymerization.
Alkylene oxides such as ethylene oxide, propylene oxide and 1,2-butylene oxide are polymerized to form a wide variety of polyether products. For example, polyether polyols are prepared in large quantities for polyurethane applications. Other polyethers are used as lubricants, brake fluids, compressor fluids, and many other applications.
These polyethers are commonly prepared by polymerizing one or more alkylene oxides in the presence of an initiator compound and a catalyst. Recently, the so-called double metal cyanide (DMC) catalysts have been used commercially as polymerization catalysts for alkylene oxides. These catalysts are described, for example, in U.S. Pat. Nos. 3,278,457, 3,278,458, 3,278,459, 3,404,109, 3,427,256, 3,427,334, 3,427,335, 5,470,813 among many others. Although these catalysts are described very broadly in the patent literature, only a limited number of forms of the catalyst have been shown to be active alkylene oxide polymerization catalysts.
The active catalysts are typically prepared by mixing an excess of a water soluble salt of a metal M with a water soluble compound containing an anion of the type M1[(CN)r(X)t], in aqueous solution. An excess of the M salt is essential to produce an active catalyst. In addition, the active forms of the catalyst all require the presence of an organic complexing agent. In conventional processes, this is provided by either adding the complexing agent to one or both of the starting solutions or by separately adding the complexing agent immediately after mixing the starting solutions. A catalyst complex containing the insoluble Mb[M1(CN)r(X)t]c associated with the complexing agent and bound water, precipitates and is washed, usually multiple times, with mixtures of the complexing agent and water.
The preparation method just described has several disadvantages. First, the variety of compositions that can be made is usually limited to those having a single type of M ion.
Second, because the salt of the metal M is water-soluble, at least a portion of the excess salt remains in the aqueous phase when the catalyst complex first precipitates. This salt is lost when the precipitated catalyst is isolated. Thus, some of the salt is wasted, and, unless the product is subsequently analyzed, it is often not known how much of the excess salt is incorporated into the catalyst. This can be important, as it is believed that the activity of the catalyst complex depends on the presence of an excess of the salt.
In addition, the preparation method described above uses much more of the complexing agent compound than actually becomes bound into the catalyst complex. This results in excess raw material costs and increases the overall cost of making the catalyst complex.
Thus, it would be desirable to provide a method by which controlled amounts of excess metal salt can be incorporated into a metal-containing cyanide catalyst. It would further be desirable to provide a less expensive method of making these metal-containing catalyst complexes, and to reduce the quantities of raw materials and the number of steps required to prepare these catalyst complexes.
In one aspect, this invention is a method for preparing a metal-containing catalyst, comprising the steps of:
a) forming a first solution of a metal salt in water;
b) forming a second aqueous solution of a metal cyanide compound or a mixture thereof with a supplementary compound having a transition metal-containing anion which forms an insoluble salt with the metal in said metal salt;
c) mixing said first and second solutions in proportions such that no more than a stoichiometric quantity of the metal salt is present in the mixture, based on the number of equivalents of the metal cyanide compound and any supplementary compound present, under conditions such that the metal salt, the metal cyanide salt and the supplementary compound, if present, react to form an insoluble precipitate;
wherein step c) is performed in the presence of an organic complexing agent compound, step c) is followed by washing the insoluble precipitate with an organic complexing agent compound, or both, then
d) removing excess water and any excess organic complexing agent from the insoluble precipitate to form an isolated precipitate; and
e) mixing the isolated precipitate with an impregnating solution containing an additional quantity of a metal salt dissolved in water or a mixture of water and a soluble organic complexing agent, under conditions such that the impregnating solution is substantially absorbed by the isolated precipitate, wherein the concentration of the metal salt in the impregnating solution is such that about 0.1 to about 1.5 moles of metal salt are provided in said impregnating solution per mole of metal cyanide compound and transition metal-containing anion in the isolated precipitate.
The method of the first aspect of the invention provides a convenient way to make metal-containing catalyst complexes having a controlled content of excess metal salt. The method further avoids or minimizes losses of the metal salt during washing steps.
In another aspect, this invention is a method for preparing a metal-containing catalyst, comprising the steps of:
a) forming a first solution of a metal salt in water;
b) forming a second aqueous solution of a metal cyanide compound or a mixture thereof with a supplementary compound having a transition metal-containing anion which forms an insoluble salt with the metal in said metal salt;
c) in the substantial absence of an organic complexing agent, mixing said first and second solutions in proportions such that no more than a stoichiometric quantity of the metal salt is present in the reaction mixture, based on the number of equivalents of the metal cyanide compound and any supplementary compound present, under conditions such that the metal salt, metal cyanide salt and supplementary compound, if present, react to form an insoluble precipitate;
d) removing excess water from the insoluble precipitate to form an isolated precipitate
e) mixing the isolated precipitate with an impregnating solution containing an additional quantity of a metal salt dissolved in a mixture of water and a soluble organic complexing agent, under conditions such that the impregnating solution is substantially absorbed by the isolated precipitate, wherein the concentration of the metal salt in the impregnating solution is such that about 0.1 to about 1.5 moles of metal salt are provided in said impregnating solution per mole of metal cyanide compound and transition metal-containing anion in the isolated precipitate.
This second aspect of the invention provides a method by which a highly active metal-containing cyanide catalyst can be prepared, using a reduced amount of organic complexing agent and with an easily controlled excess of the metal salt. The activity of this catalyst is particularly surprising because conventional preparation methods for metal-containing catalysts require the addition of copious amounts of complexing agent during the initial precipitation of the catalyst complex.
In addition, this method provides a convenient way to make specialized catalyst complexes, because different metal salts can be used to make the initial precipitate and in the impregnating solution.
In a third aspect, this invention is a method for preparing a metal-containing cyanide catalyst, comprising the steps of:
a) forming a first solution of a metal salt in water;
b) forming a second aqueous solution of a metal cyanide compound or a mixture thereof with a supplementary compound having a transition metal-containing anion which forms an insoluble salt with the metal in said metal salt;
c) mixing said first and second solutions in proportions such that no more than a stoichiometric quantity of the metal salt is present in the reaction mixture, based on the combined number of equivalents of the metal cyanide compound and supplementary compound, if any, under conditions such that the metal salt, metal cyanide salt and supplementary compound, if present, react to form an insoluble precipitate;
d) removing excess water from the insoluble precipitate to form an isolated precipitate; and
e) mixing the isolated precipitate with an impregnating solution containing an additional quantity of a metal salt dissolved in a mixture of water and a soluble organic complexing agent, wherein the concentration of the metal salt in the impregnating solution is such that about 0.1 to about 1.5 moles of metal salt are provided in said impregnating solution per mole of metal cyanide compound and transition metal-containing anion in the isolated precipitate.
In yet another aspect, this invention is a metallic cyanide catalyst of the structure:
Mb[M1 (CN)r(X)t]c[M2(X)6]d.zL.aH2O.nM3xAy,
wherein M is a metal ion that forms an insoluble precipitate with the M1(CN)r(X)t group and which has at least one water soluble salt;
M1 and M2 are transition metal ions that may be the same or different;
X represents a group other than cyanide that coordinates with an M1 or M2 ion;
L represents an organic complexing agent;
M3xAy represents a water-soluble salt of metal ion M3 and anion A, wherein M3 is different than M;
b and c are positive numbers that, together with d, reflect an electrostatically neutral complex;
d is zero or a positive number;
x and y are numbers that reflect an electrostatically neutral salt;
r is from 4 to 6; t is from 0 to 2; and
z, n and a are positive numbers (which may be fractions) indicating the relative quantities of the complexing agent, water molecules and M3xAy, respectively.
The metal-containing cyanide catalyst of this invention can be represented by the general formula:
Mb[M1 (CN)r(X)t]c[M2(X)6]d.zL.aH2O.nM3xAy,
wherein M is a metal ion that forms an insoluble precipitate with the M1(CN)r(X)t group and which has at least one water soluble salt;
M1 and M2 are transition metal ions that may be the same or different;
each X independently represents a group other than cyanide that coordinates with an M1 or M2 ion;
L represents an organic complexing agent;
M3xAy represents a water-soluble salt of metal ion M3 and anion A, wherein M3 is different than M;
b and c are positive numbers that, together with d, reflect an electrostatically neutral complex;
d is zero or a positive number;
x and y are numbers that reflect an electrostatically neutral salt;
r is from 4 to 6; t is from 0 to 2; and
z, n and a are positive numbers (which may be fractions) indicating the relative quantities of the complexing agent, water molecules and M3xAy, respectively.
The X groups in any M2(X)6 do not have to be all the same. The molar ratio of c:d is advantageously from about 100:0 to about 20:80, more preferably from about 100:0 to about 50:50, and even more preferably from about 100:0 to about 80:20.
The term xe2x80x9cmetal saltxe2x80x9d is used herein to refer to a salt of the formula MxAy or M3xAy, where M, M3, x, A and y are as defined above.
M and M3 are preferably metal ions selected from the group consisting of Zn+2, Fe+2, Co+2, Ni+2, Mo+4, Mo+6, Al+3, V+4, V+5, Sr+2, W+4, W+6, Mn+2, Sn+2, Sn+4, Pb+2, Cu+2, La+3 and Cr+3. M and M3 are more preferably Zn+2, Fe+2, Co+2, Ni+2, La+2 and Cr+3. M is most preferably Zn+2.
Suitable anions A include halides such as chloride and bromide, nitrate, sulfate, carbonate, cyanide, oxalate, thiocyanate, isocyanate, perchlorate, isothiocyanate, and a C1-4 carboxylate. Chloride ion is especially preferred.
The term xe2x80x9cmetal cyanide compoundxe2x80x9d is used herein to refer to a compound as represented by the structure Bu[M1(CN)r(X)t]v, where B represents hydrogen or a metal atom that forms a water soluble salt with the M1(CN)r(X)t group, u and v are integers that reflect an electrostatically neutral salt, and M1, r, X and t are as defined before. B is preferably hydrogen or an alkali metal such as lithium, potassium, sodium or cesium.
The term xe2x80x9csupplementary compoundxe2x80x9d is used herein to refer to a compound having the general structure Bu[M2(X)6]v, where B, M2, X, u and v are as defined before. The use of a supplementary compound is optional in this invention.
M1 and M2 are preferably Fe+3, Fe+2, Co+3, Co+2, Cr+2, Cr+3, Mn+2, Mn+3, Ir+3, Ni+2, Rh+3, Ru+2, V+4 and V+5. Among the foregoing, those in the plus-three oxidation state are more preferred. Co+3 and Fe+3 are even more preferred and Co+3 is most preferred.
Preferred groups X include anions such as halide (especially chloride), hydroxide, sulfate, C1-4 carbonate, oxalate, thiocyanate, isocyanate, isothiocyanate, C1-4 carboxylate and nitrite (NO2xe2x88x92) and uncharged species such as CO, H2O and NO. Particularly preferred groups X are NO, NO2xe2x88x92and CO.
The catalyst is complexed with an organic complexing agent. A great number of complexing agents are potentially useful, although catalyst activity may vary according to the selection of a particular complexing agent. Examples of such complexing agents include alcohols, aldehydes, ketones, ethers, amides, nitriles, sulfides, and the like.
Suitable alcohols include monoalcohols and polyalcohols. Suitable monoalcohols include methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, t-butanol, octanol, octadecanol, 3-butyn-1-ol, 3-butene-1-ol, propargyl alcohol, 2-methyl-2-propanol, 2-methyl-3-butyn-2-ol, 2-methyl-3-butene-2-ol, 3-butyn-1-ol, 3-butene-1-ol, 1-t-butoxy-2-propanol and the like. Suitable monoalcohols also include halogenated alcohols such as 2-chloroethanol, 2-bromoethanol, 2-chloro-1-propanol, 3-chloro-1-propanol, 3-bromo-1-propanol, 1,3-dichloro-2-propanol, 1-chloro-2-methyl-2-propanol as well as nitroalcohols, keto-alcohols, ester-alcohols, cyanoalcohols, and other inertly substituted alcohols.
Suitable polyalcohols include ethylene glycol, propylene glycol, glycerine, 1,1,1-trimethylol propane, 1,1,1-trimethylol ethane, 1,2,3-trihydroxybutane, pentaerythritol, xylitol, arabitol, mannitol, 2,5-dimethyl-3-hexyn-2,5-diol, 2,4,7,9-tetramethyl-5-decyne-4,7-diol, sucrose, sorbitol, alkyl glucosides such as methyl glucoside and ethyl glucoside, and the like. Low molecular weight polyether polyols, particular those having an equivalent weight of about 350 or less, more preferably about 125-250, are also useful complexing agents.
Suitable aldehydes include formaldehyde, acetaldehyde, butyraldehyde, valeric aldehyde, glyoxal, benzaldehyde, toluic aldehyde and the like. Suitable ketones include acetone, methyl ethyl ketone, 3-pentanone, 2-hexanone and the like.
Suitable ethers include cyclic ethers such as dioxane, trioxymethylene and paraformaldehyde as well as acyclic ethers such as diethyl ether, 1-ethoxy pentane, bis(betachloro ethyl) ether, methyl propyl ether, diethoxy methane, dialkyl ethers of alkylene or polyalkylene glycols (such as ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether and octaethylene glycol dimethyl ether), and the like.
Amides such as formamide, acetamide, propionamide, butyramide and valeramide are useful complexing agents. Esters such as amyl formate, ethyl formate, hexyl formate, propyl formate, ethyl acetate, methyl acetate, triethylene glycol diacetate and the like can be used as well. Suitable nitriles include acetonitrile, proprionitrile and the like. Suitable sulfides include dimethyl sulfide, diethyl sulfide, dibutyl sulfide, diamyl sulfide and the like.
Preferred complexing agents are t-butanol, 1-t-butoxy-2-propanol, polyether polyols having an equivalent weight of about 75-350 and dialkyl ethers of alkylene and polyalkylene glycols. Especially preferred complexing agents are t-butanol, 1-t-butoxy-2-propanol, polyether polyols having an equivalent weight of 125-250 and a dimethyl ether of mono-, di- or triethylene glycol. t-Butanol and glyme (1,2-dimethoxy ethane) are most preferred.
In addition, the catalyst complex contains a quantity of water that is bound into the crystalline lattice of the complex. Although the amount of bound water is difficult to determine, it is believed that this amount is from about 0.25 to about 3 moles of water per mole of M1 and M2 ions.
In the method of the first aspect of the invention, separate aqueous solutions of the metal salt and the metal cyanide compound are formed. The aqueous solutions may contain, in addition to the water and metal salt or metal cyanide compound, a quantity of a mineral acid or a buffer to adjust the pH of the solution in order to more readily dissolve the metal salt and metal cyanide compounds. In the first aspect of the invention, either or both of the solutions may contain an organic complexing agent or a polyether compound, as described before.
In this first aspect, the solution of the metal salt and the solution of metal cyanide compound (optionally containing a supplementary compound) are then mixed with agitation at proportions such that no more than a stoichiometric quantity of the metal salt is provided, based on the equivalents of the metal cyanide compound (and supplementary compound, if present). The solutions can be mixed in any order. However, it is most preferred to add the solution of the metal cyanide compound to that of the metal salt. This tends to reduce the amount of undesirable ions that are trapped in the complex. By xe2x80x9cstoichiometric quantityxe2x80x9d, it is meant that the metal salt is present in more than a 5 equivalent- % excess, preferably in no more than a 2 equivalent- % excess, more preferably in no more than a 1 equivalent- % excess, based on the amount of metal cyanide compound plus any supplementary compound. It is most preferred that the number of equivalents of metal salt be approximately equal to the number of equivalents of metal cyanide compound, plus any supplementary compound that may be present.
A precipitate forms when the solutions are mixed. The precipitate corresponds to the structure
Mb[M1(CN)r(X)t]c[M2(X)6]d.aH2O
where M, M1, X, a, b, c, d, r and t are as defined before. If one or both of the starting solutions contains an organic complexing agent, the precipitate will also contain a quantity of bound complexing agent molecules.
The resulting precipitate is then isolated from the water by filtration, centrifugation or other suitable process. In the first aspect of the invention, the precipitate is preferably washed one or more times with water to remove occluded ions such as those designated by B and X in the forgoing formulae. It is particularly preferred to remove any alkali metal and halide ions from the precipitated complex to as low a level as reasonably possible. In the method of the first aspect of the invention, if neither of the starting solutions contains an organic complexing agent, one or more of the subsequent washes must contain a quantity of the complexing agent. However, if the complexing agent is present in one or both of the starting solutions, its use is optional in the subsequent washings. When a complexing agent is used in the washes, it advantageously constitutes from about 10 to about 100 wt. % of the wash solution. A convenient method of performing the washes is to wash the precipitate multiple times, gradually increasing the complexing agent content of the wash solution, so that the final wash is 100 wt. % complexing agent.
The precipitate is then dried to remove excess water, and excess complexing agent if one or more of the washes also contains the complexing agent. This is conveniently done by heating the precipitate under vacuum at a somewhat elevated temperature, such as about 35 to about 95xc2x0 C., preferably about 45-75xc2x0 C., until the precipitate reaches a constant weight. The resulting product is the isolated precipitate.
The isolated precipitate is then impregnated with a solution of a metal salt, M3xAy, in water. In the first aspect of the invention, this impregnating solution may also contain one or more complexing agent compounds. The impregnating solution may, if desired, also contain a polyether, especially a poly(propylene oxide) of up to about 4000 molecular weight. The impregnation is easily done with simple mixing at any convenient temperature, preferably about room temperature. Enough of the impregnating solution is used to deliver a sufficient amount of the metal salt to form an active catalyst complex. Typically, from about 0.1, preferably from about 0.25, to about 1.5, preferably to about 1.0, more preferably to about 0.75, moles of excess metal salt per mole of M1 and M2 ion is sufficient to form an active complex. When M3xAy is zinc chloride, these amounts correspond to about 9 to about 30, preferably about 11 to about 25, parts by weight of zinc chloride per 100 parts by weight of the isolated precipitate.
In addition, it is preferred that the amount does not exceed that amount of solution that can be substantially absorbed by the precipitate. The amount of the solution that can be absorbed will vary according to the chemical composition of the isolated precipitate and its porosity. A typical amount of solution to be used is from about 0.5 to about 2, preferably about 0.8 to about 1.5, more preferably about 1 to about 1.5, milliliters of solution per gram of isolated precipitate.
In the first aspect of the invention, the impregnating solution advantageously contains water and complexing agent in a weight ratio of about 100:0 to about 10:90, preferably about 90:10 to about 30:70.
Note that the metal salt used in the impregnating solution does not have to be the same metal salt that is used in the initial precipitation step. In particular, the respective metal salts may contain different metals. Thus, for example, a zinc salt may be used in the precipitation step, but a salt of lanthanum, chromium, iron or other metal can be used in the impregnation step. Because different metal salts can be used in the method of the invention, this method provides a method by which catalyst complexes can be tailored for specific applications.
After the isolated catalyst is mixed with the impregnating solution, the mixture typically has a thick, mud-like consistency.
The method of the first aspect of the invention provides the advantages of permitting control over the amount of excess metal salt introduced into the catalyst complex and in some instances reducing the quantity of metal salt that is needed.
The second aspect of the invention is similar, except that no complexing agent is introduced into the system until the impregnating solution is added to the isolated precipitate. That is, neither of the starting solutions contains an organic complexing agent, and preferably does not contain a polyether or other organic species, either. The precipitate that is formed from the starting solutions thereof is substantially free of organic complexing agent. Moreover, in the second aspect of the invention, the subsequent washings of the precipitate are done with a wash solution that is devoid of complexing agent, polyether polyol and other organic species, so that the isolated precipitate remains substantially devoid of those materials.
In the method of the second aspect, the impregnating solution contains, in addition to water and the metal salt, an amount of organic complexing agent and optionally a polyether or other desirable organic species. In this second aspect, the impregnating solution advantageously contains water and complexing agent in a weight ratio of about 90:10 to about 10:90, preferably about 70:30 to about 30:70. As before, it is preferred that no more solution is used than can be substantially absorbed by the isolated precipitate.
The method of the second aspect provides the additional advantages of substantially reducing the amount of complexing agent that is used in the process, and of simplifying the catalyst preparation. Like the method of the first aspect, the method of the second aspect provides for controlled introduction of predetermined amounts of excess metal salts into the catalyst complex.
In either aspect of the invention, the impregnated catalyst is preferably permitted to sit at approximately ambient conditions (room temperature, atmospheric pressure) for a period to permit the metal salt and complexing agent to become bound into the catalyst complex. This process is typically completed in a few hours at ambient conditions. If desired, slightly elevated temperatures and/or slightly decreased pressures may be applied to accelerate the process. Then, the catalyst preferably is dried under vacuum and/or more elevated temperatures to complete the drying process.
Further, in either aspect of the invention, the impregnation step can be carried out in two or more stages. Thus, after a first impregnation step is performed, the complexing agent is allowed to become bound into the complex, and the complex dried, as before. Then, a second impregnation step is performed and the impregnated catalyst worked up and dried as described before. Further impregnation steps can be done in similar manner. The use of multiple impregnations is desirable when a high loading of the M3xAy salt is desired, or when the M3xAy is not highly soluble in the impregnating solution.
Preferred catalysts that can be prepared by the methods of the invention include:
Zinc hexacyanocobaltate.zL.aH2O.nZnCl2;
Zn[Co(CN)5NO].zL.aH2O.nZnCl2;
Zns[Co(CN)6]o[Fe(CN)5NO]p.zL.aH2O.nZnCl2 (o, p=positive numbers, s=1.5o+p);
Zns[Co(CN)6]o[Co(NO2)6]p[Fe(CN)5NO]q.zL.aH2O.nZnCl2 (o, p, q=positive numbers, s=1.5(o+p)+q);
Zinc hexacyanocobaltate.zL.aH2O.nLaCl3;
Zn[Co(CN)5NO].zL.aH2O.nLaCl3;
Zn[Co(CN)6]o[Fe(CN)5NO]p.zL.aH2O.nLaCl3 (o, p=positive numbers, s=1.5o+p);
Zns[Co(CN)6]o[Co(NO2)6]p[Fe(CN)5NO]q.zL.aH2O.nLaCl3 (o, p, q=positive numbers, s=1.5(o+p)+q);
Zinc hexacyanocobaltate.zL.aH2O.nCrCl3;
Zn[Co(CN)5NO].zL.aH2O.nCrCl3;
Zns[Co(CN)6]o[Fe(CN)5NO]p.zL.aH2O.nCrCl3 (o, p=positive numbers, s=1.5o+p);
Zns[Co(CN)6]o[Co(NO2)6]p[Fe(CN)5NO]q.zL.aH2O.nCrCl3 (o, p, q=positive numbers, s=1.5(o+p)+q);
Magnesium hexacyanocobaltate.zL.aH2O.nZnCl2;
Mg[Co(CN)5NO].zL.aH2O.nZnCl2;
Mgs[Co(CN)6]o[Fe(CN)5NO]p.zL.aH2O.nZnCl2 (o, p=positive numbers,s=1.50+p);
Mgs[Co(CN)6]o[Co(NO2)6]p[Fe(CN)5NO]q.zL.aH2O.nZnCl2 (o, p, q=positive numbers, s=1.5(o+p)+q);
Magnesium hexacyanocobaltate.zL.aH2O.nLaCl3;
Mg[Co(CN)5NO].zL.aH2O.nLaCl3;
Mgs[Co(CN)6]o[Fe(CN)5NO]p.zL.aH2O.nLaCl3 (o, p=positive numbers, s=1.5o+p);
Mgs[Co(CN)6]o[Co(NO2)6]p[Fe(CN)5NO]p.zL.aH2O.nLaCl3 (o, p, q=positive numbers, s=1.5(o+p)+q);
Magnesium hexacyanocobaltate.zL.aH2O.nCrCl3;
Mg[Co(CN)5NO].zL.aH2O.nCrCl3;
Mgs[Co(CN)6]o[Fe(CN)5NO]p.zL.aH2O.nCrCl3 (o, p=positive numbers, s=1.5o+p);
Mgs[Co(CN)6]o[Co(NO2)6]p[Fe(CN)5NO]q.zL.aH2O.nCrCl3 (o, p, q=positive numbers, s=1.5(o+p)+q); as well as the various complexes such as are described at column 3 of U.S. Pat. No. 3,404,109, incorporated herein by reference.
The catalyst complex of the invention is used to polymerize alkylene oxides to make polyethers. In general, the process includes mixing a catalytically effective amount of the catalyst with an alkylene oxide under polymerization conditions, and allowing the polymerization to proceed until the supply of alkylene oxide is essentially exhausted. The concentration of the catalyst complex is selected to polymerize the alkylene oxide at a desired rate or within a desired period of time. The amount of catalyst complex is conveniently expressed in terms of its weight in parts per million of the product polyether. The weight of the product polyether is itself generally regarded as the combined weight of initiator plus monomers. Thus, a suitable amount of catalyst is from about 5 to about 10,000 parts by weight catalyst complex per million parts combined weight of alkylene oxide, and initiator and comonomers, if present. More preferred catalyst levels are from about 10, especially from about 25, to about 500, more preferably about 100 ppm, most preferably about 50 ppm, on the same basis.
For making high molecular weight monofunctional polyethers, it is not necessary to include an initiator compound. However, to control molecular weight, impart a desired functionality (number of hydroxyl groups/molecule) or a desired functional group, an initiator compound is preferably mixed with the catalyst complex at the beginning of the reaction. Suitable initiator compounds include monoalcohols such methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, t-butanol, octanol, octadecanol, 3-butyn-1-ol, 3-butene-1-ol, propargyl alcohol, 2-methyl-2-propanol, 2-methyl-3-butyn-2-ol, 2-methyl-3-butene-2-ol, 3-butyn-1-ol, 3-butene-1-ol and the like. Suitable monoalcohol initiator compounds include halogenated alcohols such as 2-chloroethanol, 2-bromoethanol, 2-chloro-1-propanol, 3-chloro-1-propanol, 3-bromo-1-propanol, 1,3-dichloro-2-propanol, 1-chloro-2-methyl-2-propanol and 1-t-butoxy-2-propanol as well as nitroalcohols, keto-alcohols, ester-alcohols, cyanoalcohols, and other inertly substituted alcohols. Suitable polyalcohol initiators include ethylene glycol, propylene glycol, glycerine, 1,1,1-trimethylol propane, 1,1,1-trimethylol ethane, 1,2,3-trihydroxybutane, pentaerythritol, xylitol, arabitol, mannitol, 2,5-dimethyl-3-hexyn-2,5-diol, 2,4,7,9-tetramethyl-5-decyne-4,7-diol, sucrose, sorbitol, alkyl glucosides such as methyl glucoside and ethyl glucoside and the like. However, the catalyst tends to perform better when the initiator is a polyether polyol, particularly one having an equivalent weight of about 350 or less, more preferably about 125-250.
Among the alkylene oxides that can be polymerized with the catalyst complex of the invention are ethylene oxide, propylene oxide, 1,2-butylene oxide, styrene oxide, and mixtures thereof. Various alkylene oxides can be polymerized sequentially to make block copolymers. More preferably, the alkylene oxide is propylene oxide or a mixture of propylene oxide and ethylene oxide and/or butylene oxide. Especially preferred are propylene oxide alone or a mixture of at least 50 weight % propylene oxide and up to about 50 weight % ethylene oxide.
In addition, monomers that will copolymerize with the alkylene oxide in the presence of the catalyst complex can be used to prepare modified polyether polyols. Such comonomers include oxetanes as described in U.S. Pat. Nos. 3,278,457 and 3,404,109 and anhydrides as described in U.S. Pat. Nos. 5,145,883 and 3,538,043, which yield polyethers and polyester or polyetherester polyols, respectively. Hydroxyalkanoates such as lactic acid, 3-hydroxybutyrate, 3-hydroxyvalerate (and their dimers), lactones and carbon dioxide are examples of other suitable monomers that can be polymerized with the catalyst of the invention.
The polymerization reaction typically proceeds well at temperatures from about 25 to about 150xc2x0 C. or higher, preferably from about 90-130xc2x0 C. A convenient polymerization technique involves mixing the catalyst complex and initiator, and pressuring the reactor with the alkylene oxide. Polymerization proceeds after a short induction period, as indicated by a loss of pressure in the reactor. Induction periods of from less than one minute to about 20 minutes are commonly seen, and induction periods are often less than 15 minutes. Once the polymerization has begun, additional alkylene oxide is conveniently fed to the reactor on demand, until enough alkylene oxide has been added to produce a polymer of the desired equivalent weight.
Another convenient polymerization technique is a continuous method. In such continuous processes, an activated initiator/catalyst mixture is continuously fed into a continuous reactor such as a continuously stirred tank reactor (CSTR) or a tubular reactor. A feed of alkylene oxide is introduced into the reactor and the product continuously removed.
The catalyst of this invention is especially useful in making propylene oxide homopolymers and random copolymers of propylene oxide and up to about 15 weight percent ethylene oxide (based on all monomers). The polymers of particular interest have a hydroxyl equivalent weight of from about 800, preferably from about 1000, to about 5000, preferably about 4000, more preferably to about 2500, and unsaturation of no more than 0.02 meq/g, preferably no more than about 0.01 meq/g.
The product polymer may have various uses, depending on its molecular weight, equivalent weight, functionality and the presence of any functional groups. Polyether polyols so made are useful as raw materials for making polyurethanes. Polyethers can also be used as surfactants, hydraulic fluids, as raw materials for making surfactants and as starting materials for making aminated polyethers, among other uses.
The following examples are provided to illustrate the invention, but are not intended to limit its scope. All parts and percentages are by weight unless otherwise indicated.